Electromagnet latching means for plunger

ABSTRACT

A solenoid assembly or plunger-electromagnet comprising independently wound working and auxiliary armatures; the auxiliary armature comprising a flanged, cylindrical element, coaxial with respect to the working armature and having axial movement between the working armature and the winding for operating said auxiliary armature; a fixed locking cylinder coaxial between the windings of the armatures; said working armature having axial movement within the locking cylinder, and the auxiliary armature having relative axial movement on the outer surface of the locking cylinder; spring means normally urging the auxiliary armature towards said working armature; said locking cylinder including a plurality of circumferential apertures caging therein radially-displacable rocking balls engagable between a conical stop portion of the working armature and retained thereat by the inner surface of said auxiliary armature to maintain the working armature in a fixed attitude in the absence of energization of the working armature coil; the outer surface of the working armature functioning to urge the rocking balls into abutting engagement with the auxiliary armature when the winding of the auxiliary armature is energized; both armatures being movable in common directions when their respective operating windings are energized.

United States Patent Onatsevich i 1 ELECTROMAGNET LATCHING MEANS FOR PLUNGER Mikhail Alexandrovich Onatsevich, ulitsa 6, Minusinskaya, kv. 67, Moscow, U.S.S.R.

22 Filed: Apr. 25, 1974 21 Appl.No.:464,209

[76] Inventor:

[56] References Cited UNITED STATES PATENTS 2,632,821 3/1953 Wright et al 335/l65 3,206,656 9/1965 Musgrave 335/253 FOREIGN PATENTS OR APPLICATIONS 1,035,77l 8/1958 Germany 335/253 Primary ExaminerG. Harris Allomey, Agent, or Firml-[olman & Stern [57] ABSTRACT A solenoid assembly or plunger-electromagnet com- 1 July 1,1975

prising independently wound working and auxiliary armatures; the auxiliary armature comprising a flanged, cylindrical element, coaxial with respect to the working armature and having axial movement between the working armature and the winding for operating said auxiliary armature; a fixed locking cylinder coaxial between the windings of the armatures; said working armature having axial movement within the locking cylinder, and the auxiliary armature having relative axial movement on the outer surface of the locking cylinder; spring means normally urging the auxiliary armature towards said working armature; said locking cylinder including a plurality of circumferential apertures caging therein radially-displacable rocking balls engagable between a conical stop portion of the working armature and retained thereat by the inner surface of said auxiliary armature to maintain the working armature in a fixed attitude in the absence of energization of the working armature coil; the outer surface of the working armature functioning to urge the rocking balls into abutting engagement with the auxiliary armature when the winding of the auxiliary armature is energized; both armatures being movable in common directions when their respective operating windings are energized.

2 Claims, 2 Drawing Figures ELECTROMAGNET LATCHING MEANS FOR PLUNGER FIELD OF THE INVENTION The present invention relates to electromagnets and more particularly to plunger electromagnets (solenoids) used to actuate different mechanisms, such as in tape recorder pressure rollers, braking gears and spring-loaded levers.

BACKGROUND OF THE INVENTION Known at present are plunger electromagnets (solenoids) having two windings, one thereof is a working winding, whereas the other, auxiliary winding, is a holding winding. The working winding of such electromagnets is energized by a current pulse, whereas the holding winding is designed for continuous operation. In order to draw in (energize) the armature, a current pulse is passed through the working winding, whereas current is passed through the holding winding continuously. The latter winding is energized with light current during the entire period of time the armature has to be kept in the drawn-in (energized) position. In order to return the armature back to the initial position, both windings are disconnected from the power source and de-energized. This reduces the heating of the electromagnet, to save electric energy and makes it possible to reduce the dimensions of the electromagnet. The problem, however, is not solved completely, for although the windings of the electromagnet do not consume much electric energy after the electromagnet has been in action, these windings remain connected to the power source, are heated and produce electromagnetic scattering fields.

Also known are single-winding plunger pulse electromagnets with ball locking means (cf. V. T. Kolishchuk, Ye. N. Travnikov, Konstruirovaniye i raschyotmagnitofonov /Tape Recorder Design and Calculation/, Technika publishers, Kiev, I965, pp. 2l3-223), as well as with locking means employing a rotating sprocket (cf. USSR Inventor's Certificate No. 225,498) contacting with a stationary sprocket installed in the electromagnet housing and having alternately arranged high and low teeth. Such electromagnets are actuated exclusively by current pulses. In order to draw in and release their armatures, a current pulse is passed through the same winding. Due to the first pulse, the armature is drawn in and remains in the drawn-in position due to the ball locking means or to the engagement of the rotating sprocket with the high teeth of the sprocket. The next pulse first moves the electromagnet armature slightly in the drawing-in (energized) direction; the armature is then disengaged from the electromagnet housing and released back to the retracted position as the balls roll along the grooves of the locking means, or as the rotating sprocket returns into engagement with the low teeth of the mating sprocket.

The advantage of the latter type of electromagnets, as compared to the formerone, is that their design provides a complete solution to the problem: after actuation, their windings are completely disconnected from the power source. Such electromagnets are not heated, nor do they consume excessive energy, nor do they produce electromagnetic scattering fields.

Yet the fact that the electromagnet armature is drawn in and released by identical current pulses passing through the same circuit (the electromagnets only winding) is a serious drawback, because if there are several electromagnets of this type in a device, it may happen that one or several electromagnets become dcsynchronized, so that at a moment when the armatures are to be drawn in they are released and vice versa. In addition, the locking system in such electromagnets is relatively complicated and generally unreliable.

Known is a plunger electromagnet comprising a working armature, a spring-loaded auxiliary armature and a locking means to hold the working armature in the drawn-in position with no current across the windings (c. F. T. Kolishchuk, Ye. N. Travnikov Konstruirovaniye i raschyomagnitofonov" /"Tape- Recorder Design and Calculation"/, Technical Publishers, Kiev, 1965, pp. 219 22l In fact, this electromagnet is a device consisting of two plunger single-winding electromagnets arranged perpendicularly, to each other. One of these is working electromagnet, whereas the other has a spring-loaded armature and serves as an auxiliary electromagnet. The auxiliary electromagnet actuates the locking means constructed as a simple catch connected to the armature of the auxiliary electromagnet and extending beyond the stop of the working electromagnet armature as it is drawn in,

In order to draw in the armature of the working electromagnet, a current pulse is passed through its wind ing, the armature is then drawn in. Under the action of the spring-loaded armature of the auxiliary electromagnet, the catch of the locking means engages with the stop of the working armature and holds it in the drawnin position with no current across the windings.

In order to release the armature of the working electromagnet, a current pulse is passed through the winding of the auxiliary electromagnet, the armature of the auxiliary electromagnet overcomes the force of the spring and the friction forces in the locking means, opens the catch of the locking means and releases the working armature and the latter resumes its initial position, after which the windings are again de-energized.

Although having all the advantages typical of the above-mentioned electromagents, the latter doublewinding plunger electromagnet is not free from important drawbacks.

The windings of such an electromagnet are found in different housings arranged perpendicularly to each other; for this reason, the device is quite cumbersome.

The design of the locking means is such that a substantial force is required to move it under the load of the working armature, due to which the auxiliary electromagnet differs very little, if at all, as far as its dimensions are concerned, from the working electromagnet. As the working armature is being released, the armature of the auxiliary electromagnet moves transversely to it, so that the working armature cannot start moving until the catch is completely disengaged from its stop; this decreases the response of the device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plunger electromagnet (solenoid) with reduced dimensions and energy consumption, particularly in what concerns the energy required to actuate the auxiliary electromagnet, it is also an object of the invention to improve the electromagnet response and the reliability of the locking means thereof.

The above and other objects are attained due to the fact that in a plunger electromagnet comprising a working armature, a spring-loaded auxiliary armature and a locking means to hold the working armature in the drawn-in position with no current across the windings, the auxiliary armature is made, according to the invention, in the form ofa hollow cylinder arranged coaxially with the orking armature whose end face portion, facing the auxiliary armature, is provided with a stop, whereas the locking means is also made in the form of a hollow cylinder arranged between the working armature and the auxiliary armature, at the lateral surface thereof there is at least one hole receiving a ball contacting with the stop of the working armature as it is locked in the drawn-in (energized) position.

It is preferable that the auxiliary armature be springactuated in the direction of the working armature, so that they move in the same direction as the working armature is being drawn in (energized) or released (deenergized).

The correctness of the above solution is corroborated by the fact that the dimensions and the weight of the proposed plunger electromagnet are less than those of conventional electromagnets of the same power and operating conditions; the consumption of energy required to actuate the additional armature and the locking means is reduced to a minimum; the speed of response of the proposed electromagnet is several times faster than that of conventional electromagnets.

The invention will be more fully understood from the following description of a preferred embodiment thereof when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section of the proposed elec tromagnet with the drawn-in (energized) working armature and;

FIG. 2 shows the proposed electromagnet with the working armature drawn out (dc-energized).

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the accompanying drawings, the proposed plunger electromagnet comprises a housing 1 (FIG. 1) which, apart from its general design features, plays the role of a magnetic circuit for a main electromagnet and an auxiliary electromagnet disposed in the housing. The main electromagnet comprises a working armature 2 and a winding 3 which envelops the working armature 2. The auxiliary electromagnet comprises a cylindrical, flanged auxiliary armature 4 and a winding 5 with an air gap 6 between the winding 5 and the armature 4, so that the magnetic fieid of the winding 5 causes axial motion of the armature 4 within the air gap 6.

The auxiliary armature 4 comprises a hollow cylinder arranged coaxially with the working armature 2 and has a flange 7 abutting one end of a circumposed spring 8 which acts upon the auxiliary armature 4 normally urging it in the direction of the working armature 2. Se cured at the end faces of the working armature 2 are a push rod 9 and a pull rod it) intended for connection with a mechanism (not shown), wherein they perform the work function of a drive. Secured at the push rod 9 is a shock absorber 11 made of urethane rubber, for example, and designed to absorb shocks produced by the working armature 2 as it is released under load. The

end face portion of the working armature 2, facing the auxiliary armature 4, is provided with a stop 12 made from carbon steel in the shape of a truncated cone whose generatrix forms with the base of the cone an angle which in the present embodiment is equal to 20.

Apart from the main electromagnet and the auxiliary electromagnet that have been described above, the proposed plunger electromagnet comprises a locking means comprising a hollow cylinder 13 of a diamagnetic material, which in the present case is brass, said cylinder being finally interposed between the axiallymovable auxiliary armature 4 and the working armature 2. In the lateral the ofsaid cylinder 13 are six holes 14 (only two shown) arranged symmetrically over the circumference of the cylinder, in immediate proximity to the end face thereof adjacent the working armature 2, in each hole 14 there is a ball 15.

As it has been mentioned above, the locking means i.e., cylinder 13 is disposed coaxially between the working armature 2 and the auxiliary armature 4, the armature 2 is in contact with the inner surface of the locking means 13 and is freely movable axially therein, whereas the auxiliary armature 4 is in contact with the outer sur' face of the locking means 13 and is also freely movable axially along the outer surface.

The dimensions of the holes 14, the balls 15, the locking means 13 and the thickness of the latters walls are selected so that as the working armature 2 is fixed in the drawnin (energized) position, only a small portion of the external load is applied to the inner surface of the auxiliary armature 4, the greater portion of that laod being applied to the walls of the holes 14 of the locking means 13, this takes the load off the auxiliary armature 4 and facilitates its axial movement. It should be noted in this connection that the structure of the locking means 13 enables the plunger electromagnet to withstand repeated overloads and vibrations which in no way affect the reliability of the locking of the working amature 2.

In the embodiment described herein, there are six holes 14 and, correspondingly, six balls 15, which numher is believed to be optimum for the case in question. Depending upon operating loads, the number may be either increased or reduced.

The winding 3 is wound around a combined frame having the shape of a spool, one end face portion thereof serving as a core 16 and being made of magnetically soft steel. The other end face portions 17 of the spool is also made of magnetically soft steel and is connected to the core 16 by means of an insert 18 made from a diamagnetic material, in the present case, brass. The frame with the winding 3 is fixed, by means of a threaded joint 19. to the housing 1 which is also made from magnetically soft steel.

The winding 5 is wound around a frame 20 of magnetically soft steel, said frame being rolled into the housing 1. The frame 20 is provided with an axial bore in which the pull rod 10 is movably disposed.

Thus, apart from their structural function, both frames perform the function of a magnetic circuit which is part of a greater magnetic circuit made up of the working armature 2, the frame of the winding 3 of the working armature 2 and the housing 1, as well as the auxiliary armature 4, the frame 20 and the housing 1.

The electromagnet described herein is can be disassembled. One may remove all the units from the housing 1, except the frame 20 and the winding 5, which is rolled into that housing.

If necessary. the proposed plunger electromagnet may be constructed with only one rod which may be either a push rod or a pull rod. Provision may also be made for an additional device for manual release of the working armature.

The proposed plunger electromagnet operates as follows:

in order to draw in (energized) the working armature 2, a current pulse is passed through the winding 3 as this takes place, the armature 2 moves toward the position of FIG. 1 until it abuts against the core l6, as it does so, it performs a certain amount of work. The auxiliary armature 4, whose winding 5 is de-energized at that moment, is moved by the spring 8 in the same direction as the working armature as it does so, it thrusts the balls radially into the holes 14 of the locking means and they engage step 12.

The holes M are closed by the inner wall surface of the auxiliary armature4, and the balls 15 reliably lock the working armature. Upon the end of the current pulse, the working armature 2 with its stop 12 is engaged by the balls, 13 and is reliably held by them in the drawn-in position (FIG. I) with no current passing either through the windings 3 and 5.

In order to release the working armature 2 back to the initial position (FIG. 2) a current pulse is passed only through the winding 5 of the auxiliary armature 4. Under the action of electromagnetic force, the auxiliary armature overcomes the force of the spring 8 and the friction forces and is shifted axially through space 6 along the cylinder of the locking means 13, the holes I4 are thus opened, the released balls 15 (FIG. 2) are pressed out of the open holes by the stop 12 of the working armature 2, whereas the working armature 2 resumes its initial position of FIG. 2. AS this takes place, shocks produced by the load acting upon the working cylinder 2 are absorbed by the shock absorber 4 The process of the release of the working armature 2 back to the initial position begins the moment the balls 15 start moving, i.e. before the auxiliary armature 4 completes its travel, the latter causes the proposed plunger electromagnet quick-response. The same applies to the process of drawing in and locking the working armature 2, as the auxiliary armature 4 starts moving together with the balls 15, prior to the moment the working armature 2 abuts against the core 16.

The quick response of the proposed plunger electromagnet is also quaranteed by the fact that the winding 3 and 5 of the plunger electromagnet have relatively small number of coils and, consequently, small inductance. It has become possible to reduce the number of coils of the windings 3 and 5 and, correspondingly the dimensions and the strength of the proposed electromagnet due to the fact that the permissible current density across the windings 3 and 5 is many times greater than in the case of conventional electromagnets.

The locking means 13 of the proposed electromagnet ensures reliable locking of the working armature 2 in the drawn-in position ensures its release thereof with a minimum energy consumption. Energy required for the purpose may be stored by a condenser. The latter factor is very important, since it makes it possible to release the working armature 2 to the initial position if the device wherein it is employed is disconnected from the power source in an emergency situation. In fact, the proposed plunger electromagnet can be fed from a charged condenser both for releasing and drawing in the working armature 2.

The pressure in the supply circuits of the proposed electromagnet of an energy storage capacitor makes it possible to employ low-power sources of energy which charge the energy storage condenser during intervals between current pulses. Practically the duration of current pulses required to actuate the proposed electromagnet (if the working armature is connected to a mechanism via a spring) is such that over said pulse duration the electromagnet is not heated, which substantially simplifies the problem of heat dissipation as a whole.

Also highly important, in the case the proposed electromagnet is used in tape recording devices, is the fact that when in operation, the proposed electromagnet does not produce any electromagnetic scattering fields.

The present specification is supplemented with a table of the basic technical characteristics of two versions of the proposed electromagnet. Version A is a plunger electromagnet with the working armature 2 having an end thereof in the shape of a truncated cone, as is shown in FIGs. l and 2 (over the entire travel length of the working armature the tractive effort is constant). Version B is a plunger electromagnet whose working armature has a flat end face, the rest of its components being identical to those described hereinabove (the tractive effort increases sharply as the end face of the armature approaches the core).

Table \fer- Dimensions. Weight. Tractive Clamping Working Work Actuating Supply SIOll diameter kg effort. force. stroke (mam). pulse current voltage,

and length kg kg (limit) kgm drawrelease V mrn ing a in a l. A l 6 o 27: l==6l 0.14 6.10" L? 1.6 27-48 2, B 4 3. A 4 7 1610'" o 28: 1=71 0.27 4. B [D 22.10" .3 5. A 4 9 3 I I o 34; l= 0.45 40.10" 4.5 2.l 6. B 10 7.A 040'. l= 7 H5 8. B [8 9. A o 50; l= 1.60 10 l3 140.!0" 5 0.6

What is claimed is:

l. A plunger electromagnet comprising:

a housing;

a working armature disposed in said housing for axial displacement in said housing a winding enveloping said working armature;

an auxiliary armature disposed in said housing and comprising a hollow cylinder having a flange arranged coaxially with said working armature;

a spring circumposed about said auxiliary armature in engagement between said flange and housing and spring-loading the auxiliary armature toward said working armature;

a second winding having an axial air gap between said second winding and said auxiliary armature so that the magnetic field of said second winding causes axial movement of said auxiliary armature into said air gap in opposition to said spring loading; said working armature having an end face portion facing said auxiliary armature;

a truncated-conical stop secured at said end face portion of said working armature; a locking means in said housing comprising a hollow cylinder and fixedly interposed between the path of movement of said working armature and said auxiliary armature; said cylinder including at least one hole opening radially through said cylinder for communicating with the respective path of travel of the respective armatures, a ball trapped in said hole for movement therein radially between said paths of travel, said ball being engagable with said truncated conical stop of said working armature with the inner surface of the auxiliary armature overlying the same when the working armature is energized during one attitude of operation of the plunger electromagnet, and being positionable in abutting relation with said auxiliary armature and being retained there by the outer surface of the working armature when the auxiliary armature is energized during another attitude of operation.

2. A plunger electromagnet as claimed in claim 1, wherein said auxiliary armature is spring-loaded in the direction of said working armature and said working armature is constructed and arranged with respect to said locking means for movement of both said armatures in the same direction upon energization of either the winding enveloping the working armature or energizing the second winding operating the auxiliary winding. 

1. A plunger electromagnet comprising: a housing; a working armature disposed in said housing for axial displacement in said housing a winding enveloping said working armature; an auxiliary armature disposed in said housing and comprisisng arranged coaxially with said working armature; a spring circumposed about said auxiliary armature in engagement between said flange and housing and spring-loading the auxiliary armature toward said working armature; a second winding having an axial air gap between said second winding and said auxiliary armature so that the magnetic field of said second winding causes axial movement of said auxiliary armature into said air gap in opposition to said spring loading; said working armature having an end face portion facing said auxiliary armature; a truncated-conical stop secured at said end face portion of said working armature; a locking means in said housing comprising a hollow cylinder and fixedly interposed between the path of movement of said working armature and said auxiliary armature; said cylinder including at least one hole opening radially through said cylinder for communicating with the respective path of travel of the respective armatures, a ball trapped in said hole for movement therein radially between said paths of travel, said ball being engagable with said truncated conical stop of said working armature with the inner surface of the auxiliary armature overlying the same when the working armature is energized during one attitude of operation of the plunger electromagnet, and being positionable in abutting relation with said auxiliary armature and being retained there by the outer surface of the working armature when the auxiliary armature is energized during another attitude of operation.
 2. A plunger electromagnet as claimed in claim 1, wherein said auxiliary armature is spring-loaded in the direction of said working armature and said working armature is constructed and arranged with respect to said locking means for movement of both said armatures in the same direction upon energization of either the winding enveloping the working armature or energizing the second winding operating the auxiliary winding. 